Mouldings of the type mentioned in the opening paragraph are known per se. For example, in Philips Data Handbook MA-01, 1993, page 134 a description is given of a sintered moulding in the form of a transformer core which is commercially available under the trade name 6B1. The material composition of this sintered moulding corresponds to the formula Li.sub.0.32 Zn.sub.0.43 Mn.sub.0.11 Fe.sub.2.16 O.sub.3.985.
This known moulding has the disadvantage that when it is used as a transformer core in a transformer which is operated at high frequencies, it exhibits a relatively high loss factor (V) and high overall losses (P). It has been found that the losses at room temperature are approximately 17.0 mW/cm.sup.3. This value is measured at a frequency of 3 MHz and an induction of 1 mT. These losses increase considerably when a higher induction is used or when the frequency is further increased. For example, the overall losses amount to 180 mW/cm.sup.3 at a frequency of 3 MHz and an induction of 5 mT. When said known moulding is used as a transformer core in a transformer, the high overall losses may lead to undesirable heating of the transformer. Consequently, transformer cores made from this type of material are unsuitable, in particular, for use in so-called "power" transformers. These transformers are operated at relatively high frequencies of 1 MHz or more and at relatively high inductions of 5 mT or more. In general, the expression "power applications" is to be understood to mean applications of this type of ferrite materials at frequencies in excess of 1 MHz in combination with inductions in excess of 1 mT.